Nitrogen reduction with green manure roots return maintains spring wheat yield and alleviates soil N2O emission in saline-alkali agroecosystem

The growing global demand for grain drives a greater need for nitrogen (N) input. Yet, it contributes to nitrous oxide ( N 2 O) emissions, aggravating global climate change. To tackle this dual challenge of fulfilling crop demands while maintaining or reducing N 2 O emissions, a field study was performed in wheat-green manure cropping system to assess the effects of varying fertilizer application (N100, N90 and N80: N fertilizer reduced by 0%, 10% and 20%) combined with green manure return strategy (GMR: green manure roots return, GMRS: green manure roots and shoots return), and wheat fallow after harvest (CK) on wheat yield and yield stability from 2020 to 2024, N 2 O emissions, as well as N 2 O emission intensity from 2022 to 2024. Results showed that, although N fertilizer combined with green manure return strategy increased spring wheat yield by 8%–22% by increasing soil mineral N contents, it decreased yield stability compared with CK. Soil N 2 O emissions were mainly negatively and positively regulated by pH and NO 3 − -N content in saline-alkali soil, respectively. N80 decreased cumulative soil N 2 O emission and N 2 O intensity by 20% and 10% compared with N100, respectively. Irrespective of the variations in N fertilizer levels, GMR decreased cumulative N 2 O emission and N 2 O intensity by 20%–34% and 22%–38% compared with GMRS, respectively. Overall, the findings highlighted N fertilizer reduced by 20% (160 kg N ha −1 ) with green manure roots returned in relative to normal rate (200 kg N ha −1 ) is a viable option to ensure spring wheat yield and alleviate soil N 2 O emission in saline-alkali agroecosystem. • Saline-alkali soil N 2 O emissions are regulated by NO 3 - -N and salinity conditions. • Green manure roots return alleviated N 2 O emissions than shoots and roots return. • N reduced by 20% with green manure roots return achieved agricultural sustainability.